In order to test developer beta releases, you need a paid Apple developer account. Obviously it wouldn't be great if you had to pay $99 for every device (or emp

In order to test developer beta releases, you need a paid Apple developer account. Obviously it wouldn't be great if you had to pay $99 for every device (or employee at your business) just to test on the latest beta release, so Apple allows you to register up to 100 devices on your paid developer account. Some people realized that they could sell each of those 100 slots at $5-10 to people who really wanted to use the beta (NB: previously iOS did not have public betas), hence "UDID registration". Later, some of those people realized they could also sell you the code signing certificate that's generated by the real Apple developer account; valid for up to 1 year. That means you have the option of purchasing a real code signing certificate that allows you to sideload apps on non-jailbroken iPhones.